Atomic layer controlled growth of Si 3N 4 films using sequential surface reactions

Abstract

Si 3N 4 thin films were deposited with atomic layer control on Si(100) substrates using sequential surface chemical reactions. The Si 3N 4 film growth was accomplished by separating the binary reaction 3SiCl 4+4NH 3→Si 3N 4+12HCl into two half-reactions. Successive application of the SiCl 4 and NH 3 half-reactions in an ABAB… sequence produced Si 3N 4 deposition at substrate temperatures between 500 and 900 K and SiCl 4 and NH 3 reactant pressures of 1–10 Torr. Transmission Fourier transform infrared (FTIR) spectroscopy studies indicated that the SiC 4 and NH 3 half-reactions were complete and self-limiting at substrate temperatures ≥700 K. In situ spectroscopic ellipsometry monitored the Si 3N 4 film growth versus substrate temperature and reactant exposure time. The maximum Si 3N 4 deposition rate per AB cycle was 2.45 Å per AB cycle at 700 K for reactant exposures >10 10 L. The Si 3N 4 deposition rate decreased slightly in the temperature range 700–900 K. Rutherford backscattering measurements revealed an Si/N ratio of 1:1.35 as expected for stoichiometric Si 3N 4 deposition. The surface topography of the Si 3N 4 films measured with atomic force microscopy (AFM) was nearly identical to the initial Si(100) substrate indicating extremely smooth and conformal Si 3N 4 deposition.